The invention relates to the technical field of platforms with two axles, self-propelled or otherwise, provided with a manual or automatic superelevation control.
The invention therefore concerns in particular, but not exclusively, power lift trucks of the type comprising at least a single telescopic arm, articulated in the rear half of the chassis.
Many designs of such trucks are already known in the prior art.
Reference can be made, by way of example, to the following documents:
WO-A-97/46478, WO-A-89/00972;
EP-A-0 692 448, EP-A-0 680 923, EP-A-0 656 315, EP-A-0 577 388, EP-A-0 543 276, EP-A-0 504 527, EP-A-0 433 244, EP-A-0 410 082, EP-A-0 325 064;
FR-A-2 725 191, FR-A-2 713 155, FR-A-2 624 842, FR-A-527 992;
U.S. Pat. No. 5,478,192, U.S. Pat. No. 5,198,861, U.S. Pat. No. 5,106,257, U.S. Pat. No. 4,964,778, U.S. Pat. No. 4,553,899, U.S. Pat. No. 3,937,339.
For some of these power trucks, different structures are known in the prior art, allowing the control of superelevation, manual or automatic.
For example, the document U.S. Pat. No. 3,937,339 describes a truck provided with two superelevation control jacks, disposed substantially at 90xc2x0 with respect to each other between the chassis and the front axle, an attitude measuring system allowing control of the said jacks.
The known superelevation correction systems of the prior art make it possible to maintain a suitable attitude for a four-wheel platform such as a lift truck only imperfectly.
Such is in particular the case for machines for which only one axle is swinging, the other axle being fixed.
The invention relates to a superelevation control system for a platform with two axles which does not have the drawbacks of the prior systems and also makes it possible to reduce the inclination of this platform when passing by obstacles.
To this end, the invention relates, according to a first aspect, to a superelevation correction device for a platform with two axles, the said platform comprising a chassis on which the axles are articulated, the said device being characterised in that it comprises at least one first jack articulated between the front axle and the chassis and at least one second jack articulated between the rear axle and the chassis, the two jacks being connected in parallel to the same control circuit.
According to other characteristics taken along or in combination:
the areas where the first and second jacks are articulated on the axles are situated at a distance substantially equal to the longitudinal centre axis of the platform;
the first and second jacks lying at two equal angles with respect to the vertical;
the first and second jacks lie at an angle of less than 45xc2x0 with respect to the vertical;
the chassis is articulated on the axis through two articulation areas disposed substantially half-way across the said axis;
first and second jacks are of the double-acting type;
the jack control circuit comprises a double-acting solenoid valve;
The control circuit comprises two double balancing valves (or controlled valve), ensuring safety in the event of rupture of a hose or overpressure. These valves are kept open in normal operation through a booster pressure supply (23);
the control circuit comprises a level detector or a switch.
The invention relates, according to a second aspect, to the application of a device as presented above to the correction of superelevation on lift trucks, the lift truck being in particular of the type with a telescopic arm articulated on the rear of the chassis.
Other objects and advantages of the invention will emerge from the following description of embodiments with reference to the accompanying drawing.